Alert: Armyworms in Arkansas wheat

Rick Cartwright, Arkansas Extension plant pathologist | Apr 26, 2001

Armyworm alert: Moth trap catches increased in the past week for Lonoke, Prairie, and Arkansas counties in Arkansas. Lonoke has surpassed its daily high count with 42 moths/trap/day. Numbers for Arkansas County increased to around 27 moths/trap/day while Prairie County reported only 11 moths/trap/day.

Wheat fields were scouted in each county on Thursday (April 19) of last week and several larvae were found. While the numbers were above treatment threshold in most sample areas, the larvae were still 0.25 inch or less and the cool nights this week have probably slowed development, the warm weather over the next several days should change that.

White and Monroe counties in Arkansas are still about a week behind the other counties with significant decreases in moth numbers last week.

Fields should be scouted regularly to determine any larval damage to the wheat plants. It appears from the moth catches and the presence of larvae in the fields that this will not be a year of light armyworm pressure. (Trey Reaper, Don Johnson, Gus Lorenz of the University of Arkanas Extension Service.)

Carl Hayden in Chicot County, Ark., reports major armyworm activity in the better wheat fields — starting to damage wheat foliage. Some spraying started this week and he hopes only one application will be needed. In his area, methyl parathion is the cheapest treatment followed by Tracer with Warrior being about twice as high per acre as methyl.

Ken Adams reports finding 15-20 small armyworms per sq ft in south Arkansas county today (April 25) but they are still feeding on grassy weeds. He advises watching them for a few more days as it is too early to treat yet.

Reggie Talley, Keith Perkins and Justin Hensley report small worms still feeding on grassy weeds with many fields having 3-5 worms per sq ft. Watch and wait in this area. The same appears to be true as far north as the Jonesboro area with fewer worms found further north.

Don Johnson advises waiting until threshold levels of armyworms are actually feeding on wheat before deciding about treatment. It is too early to spray these small worms feeding on Poa and other weedy grasses on the ground below the wheat canopy. At this stage, applications may not be able to reach them anyway. Also, insecticides should not be applied during the heat of the day as the worms will be low and hiding. Very early or late in the day applications should be more effective. Contact your local county agent for more advice. (Rick Cartwright)

Diseases:

Soilborne Virus: Still some symptoms hanging on in some fields.

Leaf Rust: No reports. Crop will outrun it at this point.

Stripe Rust: We found a small hotspot in one of the Pioneer Variety 26R38 plots at the Rice Research and Extension Center near Stuttgart yesterday. Still no reports elsewhere.

Septoria leaf blotch (SLB): Still mostly low on the plant. Johnnie Wheetley reports that one field of Roane wheat was at treatment threshold level this week in Poinsett County but that was it.

Fungicides: A few farmers are concerned that they decided not to use a fungicide this year, even though they usually do. Now it is too late in many fields. I say smart move and shift your concern to armyworms. Forget the diseases for this year.